1. Field of the Invention
The present invention relates to a manufacturing method for a double tube having a hole formed therein, as well as to a mold for implementing such method.
2. Description of the Related Art
Examples of a double pipe having a hole formed therein include an EGR (exhaust gas recirculation) cooling pipe, which has a construction in which a hole is formed in the outer tube of a double tube having an appropriate gap between the outer tube and the inner tube, coolant liquid is introduced into such gap via the hole, and the exhaust gas circulating inside the interior of the inner tube is cooled by this coolant liquid.
Incidentally, in the double tube having a hole formed therein described above, after the double tube 1 is formed by inserting the inner tube 1b inside the outer tube 1a, a hole 3 is formed in the outer tube 1a using a drill 2 or the like, as shown in FIG. 3(a). However, when this type of method for forming the hole 3 is used, as shown in FIG. 3(b), shavings 4 remain inside the gap 5 between the outer tube 1a and the inner tube 1b. In order to remove these shavings 4, air is blown into the gap 5 between the outer tube 1a and the inner tube 1b, and this blown air expels the shavings 4 from the gap 5.
Therefore, where this type of method for forming the hole 3 is used, not only is it troublesome to carry out the drilling using the drill 2, but it is also labor-intensive and time-consuming to remove the shavings 4, which are furthermore difficult to completely remove.